Small update_checkers() cleanup

And is a bit faster too.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

diff --git a/src/position.cpp b/src/position.cpp
index 45d0147aef1f2c6d4b244ef8ae261ebe36bc4d7a..366d61f309ed9706b0bec3d3af5797b9b8fdf48f 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -658,20 +658,18 @@ inline void Position::update_checkers(Bitboard* pCheckersBB, Square ksq, Square
   const bool Rook   = (Piece == QUEEN || Piece == ROOK);
   const bool Slider = Bishop || Rook;
 
   const bool Rook   = (Piece == QUEEN || Piece == ROOK);
   const bool Slider = Bishop || Rook;
 

+  assert(*pCheckersBB == EmptyBoardBB);
+

   // Direct checks
   // Direct checks

-  if (  (   (Bishop && bit_is_set(BishopPseudoAttacks[ksq], to))
+  if (  (   !Slider // try to early skip slide piece attacks
+         || (Bishop && bit_is_set(BishopPseudoAttacks[ksq], to))

          || (Rook   && bit_is_set(RookPseudoAttacks[ksq], to)))
          || (Rook   && bit_is_set(RookPseudoAttacks[ksq], to)))

-      && bit_is_set(attacks_from<Piece>(ksq), to)) // slow, try to early skip
-      set_bit(pCheckersBB, to);
-
-  else if (   Piece != KING
-           && !Slider
-           && bit_is_set(Piece == PAWN ? attacks_from<PAWN>(ksq, opposite_color(sideToMove))
-                                       : attacks_from<Piece>(ksq), to))
-      set_bit(pCheckersBB, to);
-
+      && bit_is_set(Piece == PAWN ? attacks_from<PAWN>(ksq, opposite_color(sideToMove)) : attacks_from<Piece>(ksq) , to))
+  {
+      *pCheckersBB = SetMaskBB[to];
+  }

   // Discovery checks
   // Discovery checks

-  if (Piece != QUEEN && bit_is_set(dcCandidates, from))
+  if (Piece != QUEEN && dcCandidates && bit_is_set(dcCandidates, from))

   {
       if (Piece != ROOK)
           (*pCheckersBB) |= (attacks_from<ROOK>(ksq) & pieces(ROOK, QUEEN, side_to_move()));
   {
       if (Piece != ROOK)
           (*pCheckersBB) |= (attacks_from<ROOK>(ksq) & pieces(ROOK, QUEEN, side_to_move()));